It is known to provide a mechanical clutch between drive and driven members by the use of interposed facially-engaged clutch plates. In usual practice the axial forces on the clutch plates are controlled or varied by means of a shift collar connected to a presser plate, and a series of coil type compression springs arranged at circumferentially spaced points around the clutch axis. The shift collar is operated in one direction to increase (or decrease) the axial force; the springs vary the axial force in the opposite direction.
One problem associated with conventional clutches arises because of wear on the clutch plates. As the clutch is operated during its normal service life the clutch plates become thinner due to the frictional wear. As a result, the force of the compression springs changes. For example, in a system wherein the springs are employed to force the clutch plates into pressure engagement any appreciable wear on the clutch plates will require an extension of the compression springs beyond their initial designed extension, thus lessening the effective force applied to the plates. The plates will therefore tend to slip on one another, with consequent increased wear and acceleration of the undesirable wear-out action.
The present invention is directed to the use of constant force, zero rate, springs as force elements in mechanical clutches. Such springs apply the same force irrespective of plate thickness changes; consequently the plates will continue to have the same engagement force throughout the expected service life. This means a lessened possibility for plate slippage and accelerated wear action.
The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without payment to me of any royalty thereon.